With the widespread use of Web based applications and the Internet in general, concerns have been raised with the availability of servers in view of malicious attacks from client devices requesting access to servers. Such attacks may include brute force attempts to access the server or so-called denial of service attacks. A denial-of-service attack (DoS attack) and distributed denial-of-service attack (DDoS attack) are attempts to make a computer server unavailable to its intended users. A denial of service attack is generally a concerted, malevolent effort to prevent an Internet site or service from functioning.
DoS and DDoS attacks typically target sites or services hosted on high-profile Web servers such as banks, credit card payment gateways and root servers. One common method of attack involves saturating the target machine with external communication connection requests such that it cannot respond to legitimate traffic, or responds so slowly as to be rendered effectively unavailable. In general terms, DoS attacks are implemented by forcing the targeted server computer to reset or consume its resources to the point of interrupting communications between the intended users and servers.
Denial of service attacks and brute force attacks depend on client devices mimicking legitimate requests to tie up server resources. In order to prevent such attacks, network firewalls may be used to intercept traffic to a networked server and attempt to filter out malicious packets. Unfortunately, many current firewalls typically cannot distinguish between legitimate requests that are originated by legitimate users and transactions that are originated by attackers.